U.S. patent application number 11/889925 was filed with the patent office on 2008-02-21 for alkaline battery.
Invention is credited to Susumu Kato, Ichiro Matsuhisa, Yasushi Sumihiro.
Application Number | 20080044730 11/889925 |
Document ID | / |
Family ID | 39101751 |
Filed Date | 2008-02-21 |
United States Patent
Application |
20080044730 |
Kind Code |
A1 |
Matsuhisa; Ichiro ; et
al. |
February 21, 2008 |
Alkaline battery
Abstract
An alkaline battery includes a positive electrode case, a
positive electrode material mixture including a hollow portion and
contacting the inner side of the positive electrode case, a gelled
negative electrode disposed in the hollow portion of the positive
electrode material mixture, a separator disposed between the
positive electrode material mixture and the gelled negative
electrode, a resin sealing body for sealing the opening of the
positive electrode case, and an alkaline electrolyte. The positive
electrode material mixture includes manganese dioxide and nickel
oxyhydroxide in a weight ratio of 20:80 to 80:20 as a positive
electrode active material. The packing density of the positive
electrode active material in the space encircled by the positive
electrode case, the separator, and the sealing body is 2.65 to 3.00
g/cm.sup.3.
Inventors: |
Matsuhisa; Ichiro; (Hyogo,
JP) ; Kato; Susumu; (Osaka, JP) ; Sumihiro;
Yasushi; (Hyogo, JP) |
Correspondence
Address: |
MCDERMOTT WILL & EMERY LLP
600 13TH STREET, NW
WASHINGTON
DC
20005-3096
US
|
Family ID: |
39101751 |
Appl. No.: |
11/889925 |
Filed: |
August 17, 2007 |
Current U.S.
Class: |
429/223 |
Current CPC
Class: |
H01M 50/166 20210101;
H01M 50/171 20210101; H01M 6/08 20130101; H01M 10/28 20130101; Y02E
60/10 20130101; H01M 2300/0085 20130101; H01M 4/32 20130101; H01M
4/76 20130101; H01M 2004/028 20130101; H01M 4/50 20130101 |
Class at
Publication: |
429/223 |
International
Class: |
H01M 4/66 20060101
H01M004/66 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 21, 2006 |
JP |
2006-224393 |
Claims
1. An alkaline battery comprising: a positive electrode case
including an opening; a positive electrode material mixture
including a hollow portion and contacting an inner side of said
positive electrode case; a gelled negative electrode disposed in
said hollow portion of said positive electrode material mixture; a
separator disposed between said positive electrode material mixture
and said gelled negative electrode; a resin sealing body for
sealing said opening of said positive electrode case; and an
alkaline electrolyte, wherein said positive electrode material
mixture includes manganese dioxide and nickel oxyhydroxide in a
weight ratio of 20:80 to 80:20 as a positive electrode active
material, and a packing density of said positive electrode active
material in a space encircled by said positive electrode case, said
separator, and said sealing body is 2.65 to 3.00 g/cm.sup.3.
2. The alkaline battery in accordance with claim 1, wherein said
packing density is 2.78 to 3.00 g/cm.sup.3.
3. The alkaline battery in accordance with claim 1, wherein said
nickel oxyhydroxide is B-nickel oxyhydroxide.
4. The alkaline battery in accordance with claim 1, wherein said
sealing body comprises nylon 6,6 or nylon 6,12.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an alkaline battery using
manganese dioxide and nickel oxyhydroxide for the positive
electrode active material.
BACKGROUND OF THE INVENTION
[0002] In alkaline batteries, a cylindrical positive electrode
material mixture is disposed in a positive electrode case also
functioning as a positive electrode terminal so that the mixture
closely contact the positive electrode case, and in the center of
the positive electrode material mixture, a gelled negative
electrode is disposed with a separator interposed therebetween.
Recently, with the load from electronic devices using such alkaline
batteries as a power source increasing, batteries excellent in
heavy-load discharge performance are desired. For improvement in
the heavy-load discharge performance, use of nickel oxyhydroxide
for the positive electrode active material has been examined.
[0003] For example, Japanese Laid-Open Patent Publication No.
2002-198060 has proposed a battery as described below. The positive
electrode material mixture containing nickel oxyhydroxide is formed
into a hollow cylindrical shape. In this positive electrode
material mixture, a negative electrode is disposed with a separator
interposed therebetween, to form an electrode body. This electrode
body is housed in a bottomed cylindrical positive electrode case,
and then the opening of the positive electrode case is sealed by
disposing a sealing body. Then, considering the expansion of nickel
oxyhydroxide contained in the positive electrode material mixture
upon overdischarge, a gap corresponding to 5 to 10% of the positive
electrode material mixture height is provided between the sealing
body and the positive electrode material mixture.
[0004] However, even when such a gap is provided, when there is a
large amount of active material in the positive electrode material
mixture, the expansion of the positive electrode material mixture
upon discharge may cause the positive electrode material mixture to
lift the sealing body up and deform the sealing body, leading to a
possibility of a leakage.
[0005] As a method for curbing the positive electrode material
mixture expansion, for example, Japanese Laid-Open Patent
Publication No. 2003-17078 has proposed that an expansion
inhibiting member is provided in the positive electrode case
between the positive electrode material mixture and the sealing
body.
[0006] However, since the space for the active material to be
charged in the positive electrode case decreases to the extent of
the volume of the expansion inhibiting member to be disposed, it is
difficult to improve discharge performance.
[0007] Thus, to solve the conventional problems as noted in the
above, the present invention aims to provide an alkaline battery in
which gas generation from overdischarge is curved, and leakage is
excellently hindered without compromising discharge capacity.
BRIEF SUMMARY OF THE INVENTION
[0008] An alkaline battery of the present invention includes:
[0009] a positive electrode case including an opening;
[0010] a positive electrode material mixture including a hollow
portion and contacting the inner side of the positive electrode
case;
[0011] a gelled negative electrode disposed in the hollow portion
of the positive electrode material mixture;
[0012] a separator disposed between the positive electrode material
mixture and the gelled negative electrode;
[0013] a resin sealing body for sealing the opening of the positive
electrode case; and
[0014] an alkaline electrolyte,
[0015] wherein the positive electrode material mixture includes
manganese dioxide and nickel oxyhydroxide in a weight ratio of
20:80 to 80:20 as a positive electrode active material, and
[0016] the packing density of the positive electrode active
material in the space encircled by the positive electrode case, the
separator, and the sealing body is 2.65 to 3.00 g/cm.sup.3.
[0017] The packing density is preferably 2.78 to 3.00
g/cm.sup.3.
[0018] The nickel oxyhydroxide is preferably B-nickel
oxyhydroxide.
[0019] The sealing body preferably includes nylon 6,6 or nylon
6,12.
[0020] The present invention achieves providing an alkaline battery
in which gas generation from overdischarge is curved, and leakage
is excellently hindered without compromising discharge
capacity.
[0021] While the novel features of the invention are set forth
particularly in the appended claims, the invention, both as to
organization and content, will be better understood and
appreciated, along with other objects and features thereof, from
the following detailed description taken in conjunction with the
drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0022] FIG. 1 is a front view of an example of an alkaline battery
of the present invention with a partially cutaway view.
[0023] FIG. 2 is a front view of a battery for evaluation with a
partially cutaway view.
DETAILED DESCRIPTION OF THE INVENTION
[0024] An alkaline battery of the present invention includes, a
positive electrode case including an opening, a positive electrode
material mixture including a hollow portion and contacting the
inner side of the positive electrode case, a gelled negative
electrode disposed in the hollow portion of the positive electrode
material mixture, a separator disposed between the positive
electrode material mixture and the gelled negative electrode, a
resin sealing body for sealing the opening of the positive
electrode case, and an alkaline electrolyte. The positive electrode
material mixture includes manganese dioxide and nickel oxyhydroxide
in a weight ratio of 20:80 to 80:20 as a positive electrode active
material. The packing density of the positive electrode active
material in the space encircled by the positive electrode case, the
separator, and the sealing body is 2.65 to 3.00 g/cm.sup.3.
[0025] Thus, an alkaline battery in which leakage is excellently
hindered can be obtained without compromising discharge
capacity.
[0026] By referring to FIG. 1, one embodiment of the present
invention is described. FIG. 1 is a front view of a cylindrical
alkaline dry battery with a partially cutaway view.
[0027] A hollow cylindrical positive electrode material mixture 2
is disposed in a bottomed cylindrical positive electrode case 1
having the bottom functioning as a positive electrode terminal, so
that the positive electrode material mixture 2 is brought in close
contact with the inner side of the cylindrical positive electrode
case 1. For the positive electrode case 1, for example,
nickel-plated steel is used. The positive electrode material
mixture 2 includes, for example, a mixture of the following:
manganese dioxide and nickel oxyhydroxide mixture powder as an
active material; graphite powder as a conductive material; and an
alkaline electrolyte. For nickel oxyhydroxide, for example,
B-nickel oxyhydroxide is used.
[0028] The average particle size of the manganese dioxide powder
is, for example, 30 to 50 .mu.m.
[0029] The average particle size of the nickel oxyhydroxide powder
is, for example, 8 to 20 .mu.m.
[0030] The average particle size of the graphite powder is, for
example, 8 to 25 .mu.m.
[0031] The weight ratio of the positive electrode active material
to the conductive material to be mixed is, for example, 95:5 to
92.5:7.5.
[0032] Inside the hollow of the positive electrode material mixture
2, a bottomed cylindrical separator 4 is disposed. Inside the
separator 4, a gelled negative electrode 3 is disposed. Further,
inside the gelled negative electrode 3, a negative electrode
current collector 6 is inserted. The gelled negative electrode 3
includes, for example, a mixture of a gelling agent such as sodium
polyacrylate, an alkaline electrolyte, and a negative electrode
active material. For the negative electrode active material, zinc
powder or zinc alloy powder is used. For the zinc alloy, for
example, a zinc alloy including Bi, In, and Al is used.
[0033] The average particle size of the zinc powder or the zinc
alloy powder is, for example, 100 to 200 .mu.m.
[0034] Used for the separator 4 is, for example, a nonwoven fabric
made by a paper-making process using mainly polyvinyl alcohol fiber
and rayon fiber. The positive electrode material mixture 2, the
gelled negative electrode 3, and the separator 4 contain an
alkaline electrolyte. For the alkaline electrolyte, for example, an
aqueous solution of potassium hydroxide or an aqueous solution of
sodium hydroxide is used.
[0035] The sealing body 5 includes, a center cylindrical portion 5a
having a through hole for inserting the negative electrode current
collector 6; an outer cylindrical portion 5b interposed between the
peripheral portion of an insulating washer 7 and of a bottom plate
8, and the opening end of the positive electrode case 1; and a
connecting portion 5c connecting the center cylindrical portion 5a
and the outer cylindrical portion 5b. The sealing body 5 is
integrated with the negative electrode current collector 6, a
bottom plate 8 also functioning as a negative electrode terminal,
and the insulating washer 7. The sealing body 5 may be obtained,
for example, by injection molding nylon. For the sealing body 5,
for example, nylon 6,6 or nylon 6,12 is used. Among these, nylon
6,12 excellent in alkali-resistance is preferably used for the
sealing body 5.
[0036] A notch 1a is provided in the proximity of the lower portion
of the opening of the positive electrode case 1, and at the upper
portion of the notch 1a, the opening end of the positive electrode
case is bent so as to cover the upper portion of the outer
cylindrical portion of the sealing body 5, and the bent portion is
crimped inwardly so as to fasten the peripheral portion of the
bottom plate 8 along with the insulating washer 7. The opening of
the positive electrode case 1 is thus sealed by the sealing body
5.
[0037] In the above embodiment, the weight ratio of manganese
dioxide to nickel oxyhydroxide to be mixed as the positive
electrode active material in the positive electrode material
mixture is 20:80 to 80:20. When the nickel oxyhydroxide content in
the positive electrode material mixture exceeds 80 parts by weight
per 100 parts by weight of the positive electrode active material
(the total of manganese dioxide and nickel oxyhydroxide), the
amount of nickel oxyhydroxide having a large volume-expansion rate
becomes large in the positive electrode material mixture to
increase the expansion rate of the positive electrode material
mixture, easily causing leakage upon overdischarge. On the other
hand, when the nickel oxyhydroxide content in the positive
electrode material mixture is below 20 parts by weight per 100
parts by weight of the positive electrode active material (the
total of manganese dioxide and nickel oxyhydroxide), the amount of
nickel oxyhydroxide in the positive electrode material mixture
decreases, declining heavy-load discharge performance.
[0038] The packing density of the positive electrode active
material (manganese dioxide and nickel oxyhydroxide) in the space
encircled by the positive electrode case 1, the separator 4, and
the sealing body 5 (hereinafter referred to as space A) is 2.65 to
3.00 g/cm.sup.3. When the packing density of the positive electrode
active material in space A is below 2.65 g/cm.sup.3, the amount of
the positive electrode active material decreases, declining
discharge performance. When the packing density of the positive
electrode active material in space A exceeds 3.00 g/cm.sup.3, the
amount of the positive electrode active material becomes large to
increase the expansion rate of the positive electrode material
mixture upon discharge, and the sealing body is pushed up outwardly
from the positive electrode material mixture expansion, easily
causing leakage upon overdischarge.
[0039] The above embodiment achieves providing an alkaline battery
in which gas generation from overdischarge is curved, and leakage
is excellently hindered without compromising discharge
capacity.
[0040] Further, the packing density of the positive electrode
active material in space A is preferably 2.78 to 3.00 g/cm.sup.3,
since discharge performance and leakage resistance further improve
based on excellent adherence of the active material powder to the
graphite powder and the optimized amount of the active material
charged.
[0041] The packing density of the positive electrode active
material in space A is obtained by using the following formula
(1).
P1=Q/R1 (1)
[0042] In the formula (1), P1 represents the packing density
(g/cm.sup.3) of the positive electrode active material in space A,
Q represents the amount of the positive electrode active material
in the positive electrode material mixture (g), and R1 represents
the volume of space A (cm.sup.3).
[0043] The volume of space A can be obtained, for example, by
comprehending the condition inside the battery by an X-ray film of
the alkaline battery.
[0044] The packing density of the positive electrode active
material in the positive electrode material mixture is preferably
2.91 to 3.21 g/cm.sup.3.
[0045] The packing density of the positive electrode active
material in the positive electrode material mixture can be obtained
by the following formula (2).
P2=Q/R2 (2)
[0046] In the formula (2), P2 represents the packing density of the
positive electrode active material in the positive electrode
material mixture (g/cm.sup.3), Q represents the amount of the
positive electrode active material in the positive electrode
material mixture (g), and R2 represents the volume of the positive
electrode material mixture (cm.sup.3).
[0047] Examples of the present invention are described in detail in
the following, but the present invention is not limited to these
Examples.
EXAMPLES 1 TO 3 AND 6, AND COMPARATIVE EXAMPLES 2, 3, AND 6
[0048] An AA alkaline dry battery as shown in FIG. 2 was made. The
battery shown in FIG. 2 was structured in the same manner as the
battery in FIG. 1 as mentioned above, except that a sealing body 15
was used instead of the sealing body 5, and a positive electrode
case 11 was used instead of the positive electrode case 1 for
easily and accurately determining the packing density of the
positive electrode active material in the space encircled by the
positive electrode case, the separator, and the sealing body. That
is, the sealing body 15 used had a flat face on the side thereof
facing the positive electrode material mixture 2 (the lower side of
an outer cylindrical portion 15b and a connecting portion 15c), the
flat face being perpendicular to the side face of the positive
electrode case 11. Unlike the positive electrode case 1, the
positive electrode case 11 had no notch 1a.
[0049] The alkaline dry battery of FIG. 2 was made as in below.
[0050] Manganese dioxide powder (average particle size: 35 .mu.m),
B-nickel oxyhydroxide powder (average particle size: 11 .mu.m), and
graphite powder (average particle size: 12 .mu.m) were mixed in a
weight ratio of 47:47:6. Further, to the obtained mixture, 1.5
parts by weight of an alkaline electrolyte in 100 parts by weight
of the mixture was added and stirred sufficiently, and then the
mixture was molded by compression to be formed into flakes. Then,
the positive electrode material mixture flakes were ground to be
formed into granules, and the granules were sieved for
classification. The granules with 10 to 100 mesh were
pressure-molded to be formed into a hollow cylindrical shape,
thereby obtaining a positive electrode material mixture pellet.
[0051] A plurality of the above positive electrode material mixture
pellets were inserted into the positive electrode case 11 (inner
diameter: 13.44 mm) and re-molded by a compression jig to obtain a
hollow cylindrical positive electrode material mixture 2 (inner
diameter: 9.0 mm) with a predetermined height. The positive
electrode material mixture 2 was brought into close contact with
the inner wall of the positive electrode case 11.
[0052] Then, the separator 4 was disposed at the side face and the
bottom face of the hollow portion of the positive electrode
material mixture 2 placed in the positive electrode case 11, and
inside the separator 4, a predetermined amount of the alkaline
electrolyte was injected. The electrolyte was absorbed into the
positive electrode material mixture 2 through the separator 4.
After a predetermined time passed, a gelled negative electrode 3
was injected in the hollow portion of the positive electrode
material mixture 2 with the separator 4 interposed
therebetween.
[0053] Used for the gelled negative electrode 3 was a gelled
negative electrode including 1 part by weight of sodium
polyacrylate as a gelling agent, 33 parts by weight of the alkaline
electrolyte, and 66 parts by weight of a negative electrode active
material. For the negative electrode active material, zinc alloy
powder including 35 ppm of Al, 250 ppm of Bi, and 500 ppm of In was
used. Used for the separator 4 was a nonwoven fabric made by a
paper-making process using mainly polyvinyl alcohol fiber and rayon
fiber. For the alkaline electrolyte, an aqueous solution of 40 wt %
sodium hydroxide was used.
[0054] Then, the negative electrode current collector 6 was
inserted into the gelled negative electrode 3. The negative
electrode current collector 6 was integrated in advance with the
sealing body 15, the bottom plate 8 also functioning as the
negative electrode terminal, and the insulating washer 7. The
sealing body 15 was obtained by injection molding nylon 6,6. Then,
the opening end of the positive electrode case 11 was crimped to
the peripheral portion of the bottom plate 8 along with the
insulating washer 7 with the sealing body 15 interposed
therebetween, to seal the opening of the positive electrode case
11. Then, the outer surface of the positive electrode case was
covered with an outer jacket, thereby obtaining an alkaline
battery. The height from the face of the positive electrode case 11
at the bottom thereof contacting the positive electrode material
mixture 2 to the face of the sealing body 15 on the side thereof
facing the positive electrode material mixture (h in FIG. 2) was 43
mm.
[0055] Upon making the above alkaline battery, the amount of the
positive electrode active material to be charged in the positive
electrode case 11, that is, the total amount of manganese dioxide
and nickel oxyhydroxide was changed variously as shown in Table 1.
The mixing weight ratio of manganese dioxide and nickel
oxyhydroxide was set to a constant value as shown in Table 1.
COMPARATIVE EXAMPLE 1
[0056] An alkaline battery was made in the same manner as Example
1, except that only manganese dioxide was used as the positive
electrode active material, and the mixing weight ratio of manganese
dioxide and graphite in the positive electrode material mixture,
and the amount of the positive electrode active material were set
to the values as shown in Table 1.
EXAMPLES 4 AND 5, AND COMPARATIVE EXAMPLES 4 AND 5
[0057] An alkaline battery was made in the same manner as Example
1, except that the mixing weight ratio of manganese dioxide and
nickel oxyhydroxide was set to the values as shown in Table 1. The
amount of the positive electrode active material to be charged in
the positive electrode case 11, that is, the total amount of
manganese dioxide and nickel oxyhydroxide was set to a constant
value as shown in Table 1.
EXAMPLES 7 AND 8
[0058] An alkaline battery was made in the same manner as Example
1, except that the mixing weight ratio of manganese dioxide, nickel
oxyhydroxide, and graphite, and the amount of the positive
electrode active material were set to the values as shown in Table
1.
COMPARATIVE EXAMPLE 7
[0059] An alkaline battery was made in the same manner as Example
8, except that the amount of the positive electrode active material
was set to the value as shown in Table 1.
EXAMPLE 9
[0060] An alkaline battery was made in the same manner as Example
1, except that for the material of the sealing body 15, nylon 6,12
was used instead of nylon 6,6.
TABLE-US-00001 TABLE 1 Positive Electrode Active Material Amount
Positive in Positive Mixing Weight Ratio of Positive Electrode
Positive Electrode Electrode Material Mixture Material Electrode
Material Materials (wt %) Mixture Material Mixture Nickel Manganese
Amount Mixture Height Oxyhydroxide Dioxide Graphite (g) (g) (mm)
Comp. 0 94 6 10.74 10.10 42.40 Ex. 1 Comp. 47 47 6 9.29 8.73 38.40
Ex. 2 Ex. 1 47 47 6 9.51 8.94 39.20 Ex. 2 47 47 6 9.96 9.36 41.00
Ex. 3 47 47 6 10.74 10.10 43.00 Comp. 47 47 6 10.91 10.26 43.00 Ex.
3 Comp. 4.7 89.3 6 10.74 10.10 42.50 Ex. 4 Ex. 4 18.8 75.2 6 10.74
10.10 42.65 Ex. 5 75.2 18.8 6 10.74 10.10 43.00 Comp. 89.3 4.7 6
10.74 10.10 43.00 Ex. 5 Ex. 6 47 47 6 10.74 10.10 41.50 Comp. 47 47
6 10.97 10.31 41.50 Ex. 6 Ex. 7 46.25 46.25 7.5 10.90 10.08 43.00
Ex. 8 47.5 47.5 5 10.60 10.07 43.00 Comp. 47.5 47.5 6 10.80 10.26
40.90 Ex. 7 Ex. 9 47 47 6 10.74 10.10 43.00
[0061] The packing density of the positive electrode active
material in the positive electrode material mixture in Table 2 was
obtained by using the above formula (2). That is, the value was the
amount of the positive electrode active material in Table 1 divided
by the volume of the positive electrode material mixture. The
volume of the positive electrode material mixture was obtained from
the height of the positive electrode material mixture in Table 1,
the inner diameter of the positive electrode material mixture (9
mm), and the inner diameter of the positive electrode case 11
(13.44 mm).
[0062] The packing density of the positive electrode active
material in space A encircled by the positive electrode case 11,
the separator 4, and the sealing body 15 in Table 2 was obtained by
using the above formula (1). That is, the value was the amount of
the positive electrode active material in Table 1 divided by the
volume of space A. The volume of space A was obtained from value h
in FIG. 2 (43 mm), the inner diameter of the positive electrode
material mixture 2 (9 mm), and the inner diameter of the positive
electrode case 11 (13.44 mm).
TABLE-US-00002 TABLE 2 Positive Electrode Active Positive Material
Electrode Packing Active Density Material In Positive Packing
Electrode Density Number of Material In Batteries in Discharge
Mixture Space A which Leakage Performance (g/cm.sup.3) (g/cm.sup.3)
Occurred Index Comp. 3.04 3.00 0 100 Ex. 1 Comp. 2.91 2.59 0 98 Ex.
2 Ex. 1 2.91 2.65 0 119 Ex. 2 2.92 2.78 0 124 Ex. 3 3.00 3.00 0 135
Comp. 3.05 3.04 5 140 Ex. 3 Comp. 3.04 3.00 0 102 Ex. 4 Ex. 4 3.02
3.00 0 132 Ex. 5 3.00 3.00 0 135 Comp. 3.00 3.00 2 135 Ex. 5 Ex. 6
3.11 3.00 0 124 Comp. 3.18 3.06 3 130 Ex. 6 Ex. 7 3.00 2.99 0 135
Ex. 8 2.99 2.99 0 134 Comp. 3.21 3.05 3 134 Ex. 7 Ex. 9 3.00 3.00 0
135
[Battery Evaluation]
(1) Discharge Performance Evaluation
[0063] A pulse discharge was carried out for each battery, by
alternating a 3 second discharge with a constant electric power of
1000 mW and a 10 second pause until the closed circuit voltage
reached 0.9 V under the 20.degree. C. environment. Then the
discharge time was obtained. Table 2 shows the results. The
discharge performance in Table 2 is shown as an index where the
discharge time of the battery in Comparative Example 1 is set as
100. Batteries are determined as excellent in discharge
performance, when the discharge time is greater by 10% or more than
the discharge time of the battery of Comparative Example 1, that
is, when the discharge performance index is 110 or more.
(2) Leakage-Resistance Evaluation
[0064] In each Example, 10 batteries were prepared, and those 10
batteries were connected in series along with a 20 O resistance to
be discharged continuously for one week under a constant
temperature environment. The batteries after the 1-week discharge
were checked if there was any leakage.
[0065] The above evaluation results are shown in Table 2.
[0066] No leakage was found in any of the batteries in Examples 1
to 3, in which the active material packing density in space A was 3
g/cm.sup.3 or less.
[0067] In the battery of Comparative Example 2, in which the active
material packing density in space A was 2.59 g/cm.sup.3, the height
of the positive electrode material mixture was low and its area of
the portion facing the gelled negative electrode was small;
therefore, the discharge performance declined more than that of the
battery in Comparative Example 1, in which only manganese dioxide
was used for the positive electrode active material. On the other
hand, in the battery of Comparative Example 3, in which the active
material packing density in space A was 3.04 g/cm.sup.3, due to the
positive electrode active material expansion, the positive
electrode material mixture could not fit in space A and caused a
sealing body distortion; therefore, leakage was found in the
battery.
[0068] The batteries of Examples 4 and 5, in which the mixing
weight ratios of nickel oxyhydroxide to manganese dioxide were
20:80 and 80:20, respectively, achieved excellent discharge
performance and leakage resistance.
[0069] However, although excellent discharge performance was
achieved in the batteries of Comparative Example 5, in which the
proportion of nickel oxyhydroxide was large, leakage occurred in
the batteries, due to the volume expansion upon discharge and the
pushing up of the positive electrode material mixture to cause
distortion in the sealing body. On the other hand, although the
batteries of Comparative Example 4 with a large proportion of
manganese dioxide achieved excellent leakage resistance, its
discharge performance was the same level with the batteries of
Comparative Example 1.
[0070] Excellent leakage resistance was achieved by the batteries
of Example 6, in which the amount of the positive electrode active
material was the same as that of the batteries of Example 3 but the
packing density of the active material in the positive electrode
material mixture was made higher than that of the batteries of
Example 3 to lower the height of the positive electrode material
mixture. However, the volume expansion of the positive electrode
material mixture upon discharge increased and leakage occurred in
the batteries of Comparative Example 6, in which the height of the
positive electrode material mixture was the same as that of the
batteries of Example 6 and the positive electrode material mixture
weight was increased so that the active material packing density
was 3.06 g/cm.sup.3, because of the large amount of the charged
positive electrode active material despite the low height of the
positive electrode material mixture.
[0071] Excellent discharge performance and leakage resistance were
achieved by the batteries of Examples 7 and 8, in which the amount
of the positive electrode active material was the same as that of
the batteries of Example 3 and the amount of graphite was
changed.
[0072] Leakage occurred in the batteries of Comparative Example 7,
in which the positive electrode active material packing density in
space A was 3.05 g/cm.sup.3, setting the mixing weight ratio in the
positive electrode material mixture to the same as that of the
batteries of Example 8; the positive electrode material mixture
weight to larger than that of the batteries of Example 8; and the
height of the positive electrode material mixture to lower than
that of the batteries of Example 8.
[0073] An alkaline battery of the present invention achieves
excellent discharge performance and leakage resistance, thus is
suitably used for a power source for electronic devices such as
communication devices and portable devices.
[0074] Although the present invention has been described in terms
of the presently preferred embodiments, it is to be understood that
such disclosure is not to be interpreted as limiting. Various
alterations and modifications will no doubt become apparent to
those skilled in the art to which the present invention pertains,
after having read the above disclosure. Accordingly, it is intended
that the appended claims be interpreted as covering all alterations
and modifications as fall within the true spirit and scope of the
invention.
* * * * *